Steve Rogers: Is everything a joke to you?
Tony Stark: Funny things are.
Steve Rogers: What's the matter? Scared of a little lightning?
Loki: I'm not overly fond of what follows.
Natasha Romanoff: This is the Tesseract, it has the potential energy to wipe out the entire planet.
Bruce Banner: What does Fury want me to do, swallow it?
[Tony zaps Banner, trying to provoke him into transforming into the Hulk.]
Steve Rogers: Are you nuts?
Tony Stark: Jury's out.
Nick Fury: There was an idea to bring together a group of remarkable people, so when we needed them, they could fight the battles that we never could.
Nick Fury: Meanwhile, is there anything about the Tesseract that we ought to know?
Steve Rogers: You should have left it in the ocean.
Jarvis: Power at 400% capacity.
Tony Stark: How about that.
[Tony jabs Bruce with a small electric prod.]
Tony Stark: Man, you have really got a lid on it, don't you? What's your secret? Mellow Jazz? Bongo Drums? Huge bag of weed?
Fighter pilot: Target aquired, target engaged.
[Hulk roars in rage and jumps to the jet.]
Fighter pilot: Target angry, target angry!
Tony Stark: If we can't protect the Earth, you can be damn sure we'll avenge it!
Tony Stark: A hero? Like you? You're a laboratory experiment, Rogers. Everything special about you came out of a bottle.
Nick Fury: You should be out celebrating. Seeing the world.
Steve Rogers: When I went under, the world was at war. I wake up, they say we won. They didn't say what we lost.
Steve Rogers: Big man in a suit of armor. Take that away and what are you?
Tony Stark: A genius billionaire playboy philanthropist.
Iron Man: Call it, Captain.
Captain America: Everybody listen up. Until we can close that portal up there, I want to use containment. Barton, I want you on that roof, eyes on everything, call out patterns and strays. Stark, you got the perimeter. Anything gets more than three blocks out, you turn it back, or you turn it to ash. Thor, you got to try and bottleneck that portal. Slow them down. You got the lighting. Light the bastards up. You and me, we stay on the ground, keep the fighting here. And Hulk... Smash.
Steve Rogers: You know, you might not be a threat, but you better stop pretending to be a hero.
Nick Fury: Until such time where the world ends, we will act like it intends to spin on.
Russian General: This is not how I wanted this evening to go.
Natasha Romanoff: I know how you wanted this evening to go. Believe me, this is better.
Answer: While Loki is not immortal, he's just as powerful as Thor, and many mortals would consider him a God as well. Loki is actually a Frost Giant taken in by Odin, but is just as invulnerable to many attacks. There may also be an element of magic involved in his survival as well.
Bishop73